1. Field
The present disclosure relates generally to wireless communications and, in particular, to wireless communications using airborne nodes. Still more particularly, the present disclosure relates to a method and apparatus for forming a communications channel with desired levels of availability and reliability using airborne nodes.
2. Background
A communications channel is a pathway between two nodes that allows information to be exchanged between these two nodes. As used herein, a “node” is a communications system configured to send and/or receive information over a communications channel. A wireless communications channel is a communications channel between two nodes that are not physically connected. For example, a wireless communications channel may be established between two ground nodes to allow these ground nodes to exchange information. The exchange of information between the two ground nodes may include one ground node sending information to and/or receiving information from the other ground node.
However, in some situations, the distance between the two ground nodes may be greater than a maximum communications range for at least one of the ground nodes. The maximum communications range for a ground node is the maximum distance from the ground node along which a communications channel having a desired bandwidth may be established with another node. As used herein, “bandwidth” is the amount of information that may be sent over a communications channel over a selected period of time. In some cases, bandwidth is identified in bits per second.
When the distance between the two ground nodes is greater than the maximum communications range for at least one of the ground nodes, one or more airborne nodes may be used to transfer information between these ground nodes. As used herein, an “airborne node” is a node located in the air between the ground and outer space. An airborne node may be implemented in, for example, an aircraft or an unmanned aerial vehicle (UAV).
For example, a first ground node may be wirelessly connected to a series of airborne nodes, which may be wirelessly connected to the second ground node. The series of airborne nodes includes one or more airborne nodes wirelessly connected to each other, with one following right after the other. The wireless connection between two nodes is typically referred to as a wireless communications link. The wireless communications links between the first ground node, the series of airborne nodes, and the second ground node form a communications channel through which information may be exchanged between the first ground node and the second ground node.
A number of factors may affect the availability and/or reliability of this communications channel. As used herein, “availability” is the ratio of the total amount of time that a communications channel is capable of being used during a given period of time to the length of that period of time. Further, “reliability”, as used herein, is the ability of the communications channel to provide the desired bandwidth within selected tolerances with respect to a specific period of time.
For example, weather conditions may affect the availability and/or reliability of the communications channel. Additionally, the communications channel may be unavailable when an aircraft on which an airborne node is implemented returns to the ground for refueling. Further, other factors, such as, for example, without limitation, altitude of the airborne nodes, the distance between each pair of adjacent airborne nodes in the series of airborne nodes, the speed of the aircraft on which an airborne node is located, and/or other suitable factors may affect the availability and/or reliability of the communications channel.
In some cases, a communications channel with a certain level of availability and a certain level of reliability may be needed for performing a number of tasks in a mission. Some currently available systems for forming communications channels using airborne nodes may be unable to form a communications channel that has the desired level of availability and the desired level of reliability. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above as well as possibly other issues.